Phase field simulation of powder bed-based additive manufacturing

Quality control in parts built layer-by-layer via Additive Manufacturing (AM) process is still a challenge since critical features, such as the control in porosity, residual stress and deformation, surface roughness and microstructure, are yet to be fully addressed. In this work, we develop a phase field model to simulate powder bed-based AM, focusing on the effects of two major process parameters, the beam power and scanning speed, on the melt pool size and shape, porosity and grain structure. The model reproduces many important phenomena observed experimentally and reveals scaling relations for the depth and length of melt pool, the porosity and the grain density on process parameters. We find critical power densities below which the grain density or the porosity increases rapidly and the grain structure is controlled by different mechanisms in different power density regimes which allows for the possibility of controlling the grain structure. The present work could serve as a useful reference for accurate control of defects and microstructure in AM build.